The present invention relates to a novel construction of an input device for use in conjunction with information processing systems such as computers. In particular, the invention is directed to improvements in a position indication device for use with a display monitor of an information processing system.
Much of the following discussion will use a computer, and particularly a personal computer workstation, as an illustrative application of the invention. However, this is not to limit the scope of application of the invention, which can be used in conjunction with a display monitor of any information processing system. Common examples of such information processing systems also include business information processing systems, entertainment systems such as the so-called computer games, and control equipment in medical, industrial and military applications.
A typical personal computer workstation includes some type of display monitor or screen which facilitates the interactive use of the computer by the user. Information typically is provided to the computer by the user through a keyboard and a position indication device. In this context, a position indication device is an input device that is controllable by the user to identify a particular position on the screen of the display monitor, move a cursor on the screen to a selected location, and the like. Examples of such a position indication device include a joystick, a track ball, and the computer "mouse".
Conventional position indication devices suffer from various disadvantages. In the case of a joystick, the user indicates a change in position on the display screen by making a corresponding movement of a lever or stick with the user's fingers. The joystick is useful to move a cursor from one position on the screen to another but is difficult to use in computer aided design (CAD) applications where the user draws shapes and lines. The joystick is found mostly in entertainment and military applications where the user must quickly move a cursor (or other screen object) into the proper position. Manipulation of a joystick involves the small muscles of the fingers that quickly fatigue.
A track ball utilizes a partially exposed ball facing the user that may be rotated by the user's hand to indicate a change in position on the display monitor screen. Manipulation of a track ball usually involves the repeated use of the user's wrist and the small muscles in the hand, thereby quickening user fatigue. Accurate positioning through the use of a track ball is more difficult compared with other position indication devices, because it is more difficult to translate a desired linear movement on the display screen into a rotational movement of the track ball. Also, a distant movement on the display screen generally requires several distinct movements of the track ball. Therefore, it is more difficult to manipulate the track ball and operate function switches at the same time.
The computer mouse typically is formed of a hand held housing through the bottom of which a rotatable, partially exposed ball protrudes, similar to the track ball construction but turned upside down. The computer mouse operates by the user rolling the mouse over a pad or other flat, generally horizontal surface. As with the track ball, the rotation of the ball in the computer mouse is translated into a corresponding repositioning, e.g., of a cursor on the screen of the display monitor.
A principal drawback of the computer mouse is the requirement of a relatively large, flat, unobstructed surface over which the mouse can be moved. In a personal computer workstation, this requirement often means that a significant portion of the user's desk must be unobstructed and dedicated as a mouse pad surface. Due to the space requirement of the pad surface for a conventional computer mouse, it has also been impractical to incorporate a mouse into a computer keyboard. Further, because the proper operation of the mouse depends on the uninterrupted rotation of the mouse ball over the pad surface, the performance of a conventional mouse degrades if the mouse ball skips or slides over the pad surface without rotation. For this reason, the conventional mouse generally is used only on a horizontal pad surface, because use of the mouse on inclined, vertical, or overhead surfaces would increase the likelihood of skipping or sliding of the mouse ball over the surface.